Massive missfire

1. liam-vtrmk1 L-plater Joined: Nov 2008 Posts: 53

   #1 25th June 2009, 21:35

   I just changed the bottom end bearings on my engine and fitted a stage 3 cylinder head and its starts ok but missfires badly when idling and when applying gentle revs although when revved quite hard it sounds perfect. ive changed the spark plugs and the coil pack is only a few months old. I really dont know what it is! i've done loads to my car and havent had it on the road for ages and this is the one thing stopping me taking it out. When the spark plugs were taken out one of them had white (oxidisation) on it which means that cyclinder was running lean maybe? if so maybe some injector cleaner and a bit off footdown up the road might sort it. Or it could be a sensor? Any ideas anyone? Help will be appreciated as i really want to sort this!
2. RichyBoiVTR Regular Poster Joined: Sep 2008 Posts: 324 mk2 8valve

   #2 25th June 2009, 23:10

   might sound silly but have you double checked your timing???
3. liam-vtrmk1 L-plater Joined: Nov 2008 Posts: 53

   #3 25th June 2009, 23:17

   im pretty sure the timings ok as when revved hard it sounds perfectly healthy.
4. Sparco_Tom Saxperience Addict Joined: Jan 2007 Aylesbury, Bucks Posts: 12836 Yeaaahh Fiesta

   #4 25th June 2009, 23:47

   bad ecu map, timing, plugs, coilpack, injectors, fuel pressure